The ability of polymorphonuclear leukocytes (PMN) to ingest and kill invading microorganisms is an important part of host defense mechanisms. PMN opsonic function is mediated in large part by surface receptors, including Fc-gamma RI/II/III (CD64, CD16, CD32w) and complement receptors 1 and 3 (CD35, CD 11b/CD 18). Using both a swine model of intra-abdominal sepsis and preliminary results from normal man, we have demonstrated an auto-oxidative effect on these receptors. Polymicrobial sepsis exacerbated this effect particularly on F-gamma RII/III. In addition, polymicrobial sepsis diminished PMN Fc-gamma R repair following oxidative injury. The purpose of this study is to determine the basis for this effect and if PMN receptor repair following oxidative injury is also impaired. To do this, our studies will involve three major components. First, the extent of auto-oxidative receptor injury will be assessed using Scatchard analyses, FACS analyses and immunofluorescence studies. These studies will serve to quantify receptor number and affinity binding constants, determine relative receptor expression and surface receptor distribution , respectively. Second, mechanisms involved in PMN oxidative receptor injury will be evaluated. These include: receptor cross-linkage/recycling, microtubular dysfunction and intra-cellular cAMP levels. Third, PMN receptor repair following oxidative injury will be investigated; specifically the role of gene transcription, protein synthesis, kinetics of repair and PMN function following receptor repair will be assayed. The above assays will be conducted on PMN adhered to components of the extra-cellular matrix (fibronectin, laminin). The rationale for this is that in states of acute infection/inflammation PMN migrate into the interstitium and adhere to these matrix proteins. The studies will first be performed in normal man followed by corroboration in the animal model. Lastly, experiments will be performed in animals with polymicrobial sepsis.